WASHINGTON — Democrats are preparing to wage a major Capitol Hill battle over highway funding this week — a fight that even they admit might not be necessary.

They launched a series of pre-emptive strikes last week intended to deter House Republicans from the same sort of political maneuvering that resulted in a partial shutdown of the Federal Aviation Administration last month.

While Republicans have given no indication they plan to use similar tactics in extending funding for all surface-transportation programs, the Democratic fears are another measure of how deep and bitter the partisan divide has become.

“I don’t count on anything going smoothly anymore,” said Sen. Barbara Boxer, D-Calif., who chairs the Environment and Public Works Committee. “For years we’ve had consensus on certain bills. Now, suddenly, with this new House and this new ideology that’s come into the Congress from the right, every single thing is a battle.”

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Beginning with the bully pulpit at the White House last week, and followed promptly by Democrats on Capitol Hill and a mass of highway lobbyists, an offensive was waged to get the GOP to acquiesce to an extension of highway funding that will expire Sept. 30.

“If we allow the transportation bill to expire, over 4,000 workers will be immediately furloughed without pay,” President Obama said in a Rose Garden appearance Wednesday. “If it’s just 10 days, it will lose nearly $1 billion in highway funding. That’s money that we can never get back, and if it’s delayed even longer, almost 1 million workers could lose their jobs over the next year. All of them would be out of a job just because of politics in Washington.”

Congress also needs to extend authority to collect the federal gas tax, which provides most of the revenue Washington spends on highway and transit projects. Without an extension, Senate Democrats said, 1.8 million transportation-related jobs would be jeopardized.

A spokesman for House Majority Leader John Boehner, R-Ohio, immediately accused Obama of “scare tactics” and said no one was suggesting that highway funding would be allowed to expire.

Rep. John Mica, the Florida Republican who was cast as the villain in the FAA funding fight last month, responded to Obama the next day.

“As chairman of the House Transportation Committee, I will agree to one additional highway program extension, this being the eighth of the overdue transportation reauthorization,” Mica said. Then he added a caveat that some Democrats said they found ominous. “I am returning to Washington to also consult with our Republican leadership before granting the 22nd FAA extension.”

The Senate buckled under House pressure on a controversial FAA extension last month.

In an effort, he said, to spur action on a long-term FAA bill, he included provisions in the House-passed extension bill that he knew the Senate wouldn’t like. He calculated that if passing extensions were not so easy, it might speed negotiations for the long-term bill.

That move infuriated senators, notably Commerce Chairman John D. Rockefeller IV, D-W.Va., who accused Republicans of “bullying” and holding the aviation system “hostage.”

With the FAA extension expiring Sept. 16 and highway funding due to run out two weeks later, wary Democrats are demanding “clean” extension bills. They fear, however, that the House may again break with tradition and add policy provisions to one or both of the bills.